High pre-treatment serum hepatitis B virus titre predicts failure of lamivudine prophylaxis and graft re-infection after liver transplantation

Antiviral therapy in patients with chronic hepatitis B and cirrhosis

Chronic hepatitis B virus infection (HBV) may result in significant morbidity, including cirrhosis, end-stage liver disease, and hepatocellular carcinoma. The management of chronic HBV cirrhosis is advancing rapidly. Current treatment options for patients with HBV-related cirrhosis include interferon-alpha (IFN-alpha), lamivudine and adefovir dipivoxil. IFN-a is used less commonly today because of its toxicity, difficulty with administration, and the availability of safer drugs. Lamivudine, an oral nucleoside analog, has proven to be at least as effective, and is safer, than IFN-a in the treatment of HBV-related cirrhosis. It is plagued by the development of resistant viral mutants, however. The newest oral nucleotide analog, adefovir dipivoxil, has shown excellent efficacy in treatment-naïve and lamivudine-resistant HBV patients and has lower rates of resistance in the short-term.

Outcome of liver transplantation for hepatitis B in the United States

Important innovations, such as hepatitis B immune globulin (HBIG) and lamivudine, have been introduced to the care of patients undergoing liver transplantation (OLT) for viral hepatitis B (HBV) (over the last 15 years). We analyzed survival of OLT recipients with HBV in the United States to examine the effect of these innovations. A retrospective analysis was conducted based on data collected prospectively by the United Network for Organ Sharing in all adult (older than 18) patients undergoing primary OLT in the United States between 1987 and 2002. OLT recipients with HBV were identified by the principal diagnosis of acute or chronic HBV or positive results on HBV markers. Patients were divided into Era 1 (1987-1991), Era 2 (1992-1996), and Era 3 (1997-2002). Era 1 consisted of 6,708 patients (675 with HBV), Era 2 consisted of 13,995 patients (1,005 with HBV), and Era 3 consisted of 20,730 patients (1,723 with HBV). More recent patients were older and had less advanced liver disease and shorter ischemic time. The survival of patients with HBV was significantly better for Era 2 than for Era 1 (P <.01) and for Era 3 than for Era 2 (P <.01). There was no difference in survival between patients with HBV and all other diagnoses for Era 3 (P =.14). In the multivariable analysis, the effect of these eras persisted when other variables such as recipient and donor age, warm ischemic time, pre-OLT disease severity, and hepatocellular carcinoma (HCC) were taken into account. Unlike previous reports, fulminant disease and Asian race had no effect on patient survival. In conclusion, these data underscore the effectiveness of therapeutic innovations that have occurred in the past two decades and indicate timely and widespread adoption of these measures by transplant centers nationwide.

Adefovir dipivoxil therapy for lamivudine-resistant hepatitis B in pre- and post-liver transplantation patients

Three-hundred and twenty-four patients were enrolled in an open-label, multicenter, international study in which pre- and post-liver transplantation (LT) patients with recurrent chronic hepatitis B (CHB) and evidence of lamivudine-resistant HBV were treated with adefovir dipivoxil 10 mg once daily. In the pre- and post-LT cohorts, 128 and 196 patients were treated for a median duration of 18.7 and 56.1 weeks, respectively. In patients who received 48 weeks of treatment, 81% of the pre-LT and 34% of the post-LT cohort achieved undetectable serum hepatitis B virus (HBV) DNA (Roche Amplicor Monitor polymerase chain reaction [PCR] assay lower limit of quantification [LLQ] < 400 copies/mL) with a median change in serum HBV DNA from baseline of -4.1 log(10) and -4.3 log(10) copies/mL, respectively. Serum alanine aminotransferase (ALT), albumin, bilirubin, and prothrombin time normalized in 76%, 81%, 50%, and 83% of pre-LT patients and 49%, 76%, 75%, and 20% of post-LT patients. The Child-Pugh-Turcotte (CPT) score improved in over 90% of patients in both cohorts. Genotypic analysis of 122 HBV baseline samples revealed that 98% of these patients had lamivudine-resistant mutant HBV. No adefovir resistance mutations were identified in patients after 48 weeks of therapy. One-year survival was 84% for pre-LT and 93% for post-LT patients (Kaplan-Meier analysis). Treatment-related adverse effects associated with adefovir dipivoxil in this setting were primarily mild to moderate in severity. In conclusion, 48 weeks of adefovir dipivoxil resulted in significant improvements in virologic, biochemical, and clinical parameters in CHB patients pre- and post-LT with lamivudine-resistant HBV.

Evolution of hepatitis B virus sequence from a liver transplant recipient with rapid breakthrough despite hepatitis B immune globulin prophylaxis and lamivudine therapy

Recurrent hepatitis B virus (HBV) infection after liver transplantation can be prevented by prophylactic hepatitis B immune globulin (HBIG) and lamivudine therapy. However, reinfection may still occur due to the emergence of immune escape mutants and mutants of the YMDD motif. The full spectrum of mutations within the HBV genome during recurrent HBV infection remains to be documented. In this study, serial HBV isolates were characterized from a patient with lamivudine resistance prior to liver transplantation who developed recurrent HBV infection within 2 months of transplantation despite a high dose of HBIG and lamivudine therapy. Sequence analysis of full-length viral genome before transplantation revealed many point mutations as compared with a wild-type genotype C sequence, including the T1753G/A1762T/G1764A triple mutation in the basal core promoter and the G1896A nonsense mutation in the precore region. After transplantation and therapy, several point mutations in the HBV genome emerged or became dominant. These mutations caused L426I/L526M/M550I triple mutation (equivalent to L428I/L528M/M552I in previous reports) in the polymerase, and D144E mutation in the "a" determinant of HBsAg. Transfection experiments revealed that the D144E mutation reduced HBsAg affinity to anti-HBs, confirming its active role for immune escape. Our study suggests that mutations in the HBsAg (D144E) and the polymerase (L426I/L526M/M550I) of HBV genome may be responsible for viral breakthrough despite HBIG prophylaxis and lamivudine therapy.

Combined lamivudine and hepatitis B immunoglobulin for the prevention of hepatitis B recurrence after liver transplantation: long-term results

For the prevention of recurrent hepatitis B virus (HBV) infection after liver transplantation (LT), the efficacy of hepatitis B immunoglobulin (HBIg) has been largely demonstrated. The aim of this pilot study was to determine if the addition of lamivudine to HBIg in the prevention of HBV recurrence after LT could be more effective. Sixty HBsAg-positive/HBV DNA-negative patients underwent LT from October 1990 to December 2001. All 60 patients received intravenous HBIg to maintain serum anti-HB levels above 500 IU/L, indefinitely. Since 1997, 17 patients have received combined oral lamivudine (150 mg/day) and HBIg, and were compared with the historical cohort of 43 patients. In the historical control group, the recurrence rate was 10/43 (23%) after a 98-month median follow-up. Five patients died from HBV-related liver disease. After a 30-month median follow-up, none of the 17 patients in the combined prophylaxis group experienced HBV recurrence, and HBV DNA was undetectable by PCR in at least three serum samples per patient. HBV recurrence was significantly lower when compared with the historical control group (10/43 vs. 0/17, p < 0.01). Our results suggest that combined lamivudine and HBIg can avoid the recurrence of HBV infection in patients who are HBsAg-positive/HBV DNA negative before LT.

HBV DNA persistence 10 years after liver transplantation despite successful anti-HBS passive immunoprophylaxis

Long-term immunoprophylaxis with hepatitis B immune globulin (HBIG) is widely accepted for the prevention of recurrent hepatitis B virus (HBV) infection after liver transplantation in HBV-infected patients without viral replication. We report long-term results of HBIG administration in 284 hepatitis B surface antigen (HBsAg)-positive transplant patients. In protocol 1, 259 patients were given HBIG with the goal of maintaining the anti-HBs antibody (Ab) titer over 100 IU/L. After December 1993, 25 HBV DNA-positive patients received HBIG, with a target anti-HBs Ab titer over 500 IU/L, combined with posttransplantation antiviral therapy (protocol 2). At 10 years, 44 patients without recurrence were tested for the presence of HBV DNA in serum using real-time polymerase chain reaction (PCR); 28 were also tested in liver and peripheral blood mononuclear cells (PBMC). The overall 5- and 10-year posttransplantation actuarial rates of HBV recurrence were 24.2% and 25.4%, respectively. The 5-year recurrence rate in protocol 2 patients was 11.8%. On multivariate analysis, predictors of lower HBV recurrence risk were absence of serum HBV DNA before transplantation (P <.0001), acute liver disease (P =.0037), HDV superinfection (P =.012), and protocol 2 therapy (P <.0001). Low-level HBV DNA was detected by PCR in 45.4% of patients without HBV recurrence at 10 years. Overall actuarial 10-year survival was 74.4%. In conclusion, we confirm the efficacy of long-term HBIG immunoprophylaxis. Combination prophylaxis with HBIG and antiviral therapy is effective in patients with viral replication. Although there were only a few cases of HBV recurrence after 5 years, HBV DNA remained present in 45% of patients at 10 years.

Active immunization against de novo hepatitis B virus infection in pediatric patients after liver transplantation

The shortage of donor organs occasionally mandates the use of hepatic allografts from anti-HBc (+) donors. HBIG and/or lamivudine are recommended for the prevention of de novo HBV infection in naive patients, but there are attendant problems, such as mutant strain emergence and high cost. Active immunization presents a better alternative than the use of HBIG or lamivudine, if it can be proven to be effective. Accordingly, we investigated the outcome of HBV vaccination in pediatric hepatic transplant recipients. Between July 1999 and October 2001, 19 pediatric recipients were administered HBV vaccinations after liver transplantation at Seoul National University Hospital. Nine patients received a graft from anti-HBc (+) donors and 10 from anti-HBc (-) donors. When steroid was withdrawn, recombinant HBV vaccine was administered. The median follow-up period after vaccination was 10.0 +/- 5.2 months. Seventeen of the 19 patients showed a positive response to vaccination. In 9 patients who received grafts from anti-HBc (+) donors, 2 patients showed no response, 4 patients low response (peak HBsAb titer <1,000 IU/L), and 3 patients high response (peak HBsAb titer >/=1,000 IU/L). De novo HBV infection developed in 1 of 2 patients who showed no response to vaccination. In 10 patients who received grafts from anti-HBc (-) donors, 5 showed a low response and 5 a high response. In conclusion, HBV vaccination in pediatric patients after liver transplantation appeared to exhibit some effectiveness at protecting young children that received a graft from anti-HBc (+) donors from de novo HBV infection.

A randomized study comparing lamivudine monotherapy after a short course of hepatitis B immune globulin (HBIg) and lamivudine with long-term lamivudine plus HBIg in the prevention of hepatitis B virus recurrence after liver transplantation

BACKGROUND/AIMS

To compare the efficacy in preventing hepatitis B virus (HBV) recurrence of lamivudine vs. lamivudine plus hepatitis B immune globulin (HBIg) after a short course of HBIg and lamivudine in liver transplanted chronic hepatitis B patients.

METHODS

Forty-six patients with HBV cirrhosis received lamivudine before liver transplantation and were then randomized to receive lamivudine plus HBIg for 1 month followed by lamivudine or both drugs for 17 months.

RESULTS

Thirty-two patients were transplanted and 29 were randomized to receive combination therapy (15 cases) or lamivudine monotherapy (14 cases). HBV DNA was undetectable in all cases (17 induced by lamivudine therapy) at the time of liver transplantation. After 18 months of follow-up, all patients survived without HBV recurrence: hepatitis Bs antigen and HBV DNA were negative; however, HBV DNA was detected by polymerase chain reaction in four cases (three with HBIg plus lamivudine and one with lamivudine). Alanine aminotransferase levels were normal except in six cases (one HCV and two HDV coinfections). There were no drug-related adverse events.

CONCLUSIONS

Lamivudine monotherapy after a short course of lamivudine and HBIg is equally as efficacious in preventing HBV recurrence as HBIg plus lamivudine during the first 18 months after liver transplantation. This strategy is more economic and convenient to administer than long-term HBIg plus lamivudine.

Prevention of and treatment for hepatitis B virus infection after liver transplantation in the nucleoside analogues era

Post-transplant prophylaxis with hepatitis B immune globulin (HBIG) has significantly reduced hepatitis B virus (HBV) recurrence rates, but it is rather ineffective in patients with pretransplant viremia. Moreover, long-term HBIG administration is very expensive and may be associated with emergence of escape HBV mutants. Lamivudine has been widely used in the management of HBV transplant patients. Pretransplant lamivudine lowers HBV viremia, decreasing the risk of post-transplant HBV recurrence, but to try and minimize development of resistant HBV strains, it should start within the last 6 months of the anticipated transplantation timing. Preemptive post-transplant lamivudine monotherapy is associated with progressively increasing HBV recurrence rates, but combined therapy with lamivudine and HBIG at relatively low dosage is currently the most effective approach in this setting, even in HBV-DNA-positive patients, who also receive lamivudine in the pretransplant period. The most frequent therapy for post-transplant HBV recurrence is lamivudine, but the increasing resistance rates represent a rather challenging problem. Adefovir dipivoxil and entecavir are currently the most promising agents for lamivudine-resistant HBV strains. All these advances in anti-HBV therapy have made HBV liver disease an indication for liver transplantation irrespective of viral replication status, a complete turn around from 10 years ago.

Hepatitis B core antibody-positive grafts: recipient's risk

The transmission of hepatitis B virus infection through hepatitis B core antibody (anti-HBc)-positive liver grafts in hepatitis B surface antigen (HBsAg)-negative recipients has been established. The mandatory use of immunosuppression in transplant patients favors reactivation of latent virus that may be present in grafts from HBsAg-negative anti-HBc-positive donors. With the persistent organ donor scarcity, the use of these grafts cannot be avoided, especially in urgent cases and in areas where the prevalence of the hepatitis B virus is high, as in Asia. The recognition of posttransplant de novo hepatitis B from core antibody-positive liver donors has, therefore, led to modifications in graft allocation policies and the introduction of strategies for prophylaxis. The risk of developing this type of new-onset hepatitis B virus infection in liver transplant recipients and the various approaches to minimize this risk are reviewed. The peculiar implications of using core antibody-positive grafts in the context of living donor liver transplantation in Asia are discussed.

Recent advances in liver transplantation

Advances in liver transplantation continue to evolve but are hampered by continued increasing shortages in donor organs. This has resulted in a high incidence of patients dying while on the United Network for Organ Sharing waiting list. Indeed, we continue to assess ways of expanding the donor pool by using marginal donors, living donor liver transplantation, split liver transplantation, domino transplantation, and hepatic support systems to prolong survival long enough for the patient to undergo liver transplantation. Changes in the liver allocation policy to reduce the number of people dying while waiting for an organ are discussed. Implementation of the model for end-stage liver disease allocation system should help alleviate the problem of increasing deaths of patients while on the waiting list. Recurrent disease, particularly recurrent hepatitis C, continues to be a major problem, and effective therapy is needed to prevent both progression of hepatitis C and recurrence in the graft and avoid retransplantation. The use of pegylated interferon in combination with ribavirin holds promise for improving the success in overcoming recurrent hepatitis C. Finally, advances in immunosuppression have reduced the incidence of acute cellular rejection and chronic rejection. However, these therapies have been fraught with metabolic complications that are now affecting quality of life and long-term survival. Tailoring immunosuppressive regimens to the individual patient is discussed.

Molecular diagnosis of influenza

The past decade has seen tremendous developments in molecular diagnostic techniques. In particular, the development of PCR technology has enabled rapid and sensitive viral diagnostic tests to influence patient management. Molecular methods used directly on clinical material have an important role to play in the diagnosis and surveillance of influenza viruses. Molecular diagnostic tests that allow timely and accurate detection of influenza are already implemented in many laboratories. The combination of automated purification of nucleic acids with real-time PCR should enable even more rapid identification of viral pathogens such as influenza viruses in clinical material. The recent development of DNA microarrays to identify either multiple gene targets from a single pathogen, or multiple pathogens in a single sample has the capacity to transform influenza diagnosis. While molecular methods will not replace cell culture for the provision of virus isolates for antigenic characterisation, they remain invaluable in assisting our understanding of the epidemiology of influenza viruses.

Treatment of recurrent hepatitis B infection in liver transplant recipients

1. Therapeutic decisions are guided by a patient's clinical status (severity of disease and presence of comorbidities) and previous drug-exposure history. 2. Lamivudine is safe and effective in liver transplant recipients with recurrent hepatitis B virus (HBV) infection caused by wild-type virus or failure of hepatitis B immunoglobulin therapy. Lamivudine resistance, developing in approximately 25% after 12 months of therapy, is its main limitation. 3. Famciclovir is safe in liver transplant recipients; however, virological and clinical responses are less consistent than with lamivudine. Thus, lamivudine is favored over famciclovir as first-line therapy in transplant recipients with no previous exposure to nucleoside analogues. 4. Although limited in availability, adefovir dipivoxil appears safe and effective in treating liver transplant recipients with lamivudine-resistant HBV disease. Close monitoring of renal function is recommended, with dose adjustment in patients with reduced creatinine clearances. 5. Limited data suggest that intravenous ganciclovir, tenofovir disoproxil fumarate, and interferon alfa may be useful as rescue therapies for patients with lamivudine- or famciclovir-resistant HBV disease. 6. Antiviral therapy with two or more suitable agents may minimize the chance for viral resistance; therefore, future therapeutic strategies likely will use combination therapy in the long-term management of recurrent HBV disease.

Prevention of recurrent hepatitis B post-liver transplantation

1. Factors associated with a lower rate of recurrent hepatitis B post-liver transplantation (LT) are negative hepatitis B e antigen and/or serum hepatitis B virus DNA pre-LT, hepatitis D virus superinfection, and fulminant hepatitis B. 2. Long-term intravenous hepatitis B immune globulin (HBIG) monotherapy can reduce the overall rate of recurrent hepatitis B to 20% to 35%. 3. Long-term lamivudine monotherapy is associated with a risk for drug resistance and overall 3-year rate of recurrent hepatitis B of 40% to 50%. 4. Combination prophylaxis with HBIG and lamivudine can reduce the overall rate of recurrent hepatitis B to 0% to 10%. 5. The dose and duration of HBIG therapy needed when used in combination with lamivudine may be lower, but the optimal regimen remains to be determined. 6. Lamivudine resistance before LT is associated with an increased risk for recurrent hepatitis B post-LT. 7. A cost-effective prophylactic regimen to prevent recurrent hepatitis B should be tailored according to risk.

Hepatitis B: progress in the last 15 years

1. Patients undergoing orthotopic liver transplantation (OLT) for hepatitis B without effective prophylaxis have a high risk for recurrent infection and severe graft damage, leading to death or re-OLT. 2. Long-term prophylaxis with hepatitis B immune globulin (HBIg) significantly reduces the risk for hepatitis B virus (HBV) recurrence and increases survival. Patients with detectable HBV DNA at the time of OLT have a high risk for recurrence despite HBIg prophylaxis. 3. Lamivudine (LAM) therapy for patients with decompensated HBV cirrhosis before OLT results in inhibition of viral replication and clinical improvement. Its efficacy is limited by the frequent emergence of LAM-resistant YMDD mutations. The ideal length of therapy with LAM pre-OLT has not yet been defined. 4. Prophylaxis of HBV recurrence with LAM monotherapy is not recommended because of the reappearance of hepatitis B surface antigen after OLT in approximately 50% of patients. 5. LAM is the best available treatment for patients with established recurrent hepatitis B. Long-term therapy is associated with the emergence of drug-resistant mutants in up to 60% of patients. Severe hepatitis and liver failure have been described among liver transplant recipients with YMDD mutations. 6. Combination therapy with HBIg and LAM prevents HBV recurrence in 90% to 100% of patients who undergo OLT for hepatitis B. The optimal HBIg protocol in the LAM era is yet to be defined. 7. Preliminary studies suggest that adefovir dipivoxil inhibits HBV replication in patients infected with LAM-resistant HBV strains. 8. Fifteen years ago, hepatitis B was regarded as a relative or absolute contraindication for OLT. Today, hepatitis B is a universally accepted indication for OLT.

Factors associated with viral breakthrough in lamivudine monoprophylaxis of hepatitis B virus recurrence after liver transplantation

This study aimed to investigate the factors associated with viral breakthrough among liver transplant recipients who receive lamivudine monoprophylaxis. Consecutive patients receiving liver transplantation for HBV-related liver disease from June 1999 to October 2000 were studied. All patients received lamivudine 100 mg daily pre- and post-transplant. Serum samples were collected before lamivudine treatment, before liver transplantation, and then every 3-6 months after liver transplantation. Lamivudine-resistant mutations at the YMDD motif of HBV P gene were detected by direct sequencing and HBV DNA was quantified by real-time polymerase chain reaction (PCR). Ten patients, 7 males and 3 females, aged 50.5 +/- 7.9 years, were studied. Three patients had fulminant hepatitis and 7 patients had end-stage cirrhosis before liver transplantation. Lamivudine was started at 4.5 (range 0-40) weeks before liver transplantation. The median post-transplant follow-up was 16 (range 12-23) months. Four patients developed YMDD mutations 10.5 (0-16) months after transplantation with relapse of viraemia (median 1,294, range 51-3,135 MEq/ml). All patients who developed YMDD mutants had end-stage liver cirrhosis, and HBV DNA were detectable on the day of liver transplantation (median 0.62, range 0.086-1.63 MEq/ml). On the contrary, all 3 patients transplanted for fulminant hepatitis did not have YMDD mutation. Among the 3 end-stage cirrhotic patients who had negative HBV DNA before liver transplantation, none developed YMDD mutation. In conclusion, patients transplanted for fulminant hepatitis B and cirrhotic patients in whom HBV DNA could be rendered PCR negative before liver transplantation are unlikely to develop YMDD mutation on lamivudine monoprophylaxis.

Management of chronic viral hepatitis before and after renal transplantation

Hepatitis C virus (HCV) infection is present in 2-50% of renal transplant recipients and patients receiving hemodialysis. Renal transplantation confers an overall survival benefit in HCV positive (HCV+) hemodialysis patients, with similar 5-year patient and graft survival to those without HCV infection. However, longer-term studies have reported increased liver-related mortality in HCV-infected recipients. Unfortunately, attempts to eradicate HCV infection before transplant have been disappointing. Interferon is poorly tolerated in-patients with end-stage renal disease and ribavirin is contraindicated because reduced renal clearance results in severe hemolysis. Antiviral therapy following renal transplantation is also poorly tolerated, because of interferon-induced rejection and graft loss. Although the prevalence of hepatitis B virus (HBV) infection has declined in hemodialysis patients and renal transplant recipients since the introduction of routine vaccination and other infection control measures, it remains high within countries with endemic HBV infection (especially Asia-Pacific and Africa). Renal transplantation is associated with reduced survival in HBsAg+ hemodialysis patients. Unlike interferon, lamivudine is a safe and effective antiviral HBV treatment both before and after renal transplantation. Lamivudine therapy commenced at transplantation should prevent early posttransplant reactivation and subsequent progression to cirrhosis and late liver failure. This preemptive therapy should also eradicate early liver failure from fibrosing cholestatic hepatitis. Because cessation of treatment may lead to severe lamivudine-withdrawal hepatitis, most patients require long-term therapy. The development of lamivudine-resistance will be accelerated by immunosuppression and may result in severe hepatitis flares with decompensation. Regular monitoring with liver function tests and HBV DNA measurements should enable early detection and rescue with adefovir. Chronic HCV and HBV infections are important causes of morbidity and mortality in renal transplant recipients. The best predictor for liver mortality is advanced liver disease at the time of transplant, and liver biopsy should be considered in all potential HBsAg+ or HCV+ renal transplant candidates without clinical or radiologic evidence of cirrhosis. Established cirrhosis with active viral infection should be considered a relative contraindication to isolated renal transplantation.

Increasing applicability of liver transplantation for patients with hepatitis B-related liver disease

Liver transplantation in patients with hepatitis B has been under discussion for 20 years because of inferior results without reinfection prophylaxis; therefore, we analyzed our overall experience with liver transplantation in hepatitis B patients with immunoprophylaxis, particularly the influence of the available antiviral treatment in different periods. From 1988 to 2000, 228 liver transplants in 206 hepatitis B patients were performed. Indications were acute liver failure (10%), hepatitis B virus (HBV) cirrhosis alone (67%) or with hepatitis D virus (HDV) (13%), or hepatitis C virus (HCV) coinfection (7%). All patients received long-term immunoprophylaxis (anti-HBs > 100 U/L). HBV DNA-positive patients were treated before and after surgery with famciclovir or lamivudine since 1993 and 1996, respectively. Since 1993, antivirals also were used for HBV reinfection. The 1-, 5-, and 10-year patient survival rates were 91%, 81%, and 73%. In patients with hepatocellular carcinoma (HCC) (60% 5-year survival, P <.01) or HBV reinfection (69% 5-year survival, P <.01) survival was significantly impaired. Those with HDV or HCV coinfection had a slightly better survival than with HBV monoinfection (P >.05, not significant). Preoperative positive HBV DNA (hybridization-assay) test results were associated with a slightly impaired patient survival (78% 5-year survival, P >.05, not significant versus DNA-negative). Preoperative positive hepatitis B e antigen (HBeAg) predicted significantly worse survival (P <.05 versus negative HBeAg). Graft loss caused by reinfection was most frequent before the availability of antiviral drugs. Two-year patient survival increased from 85% in era I (1988-1993) to 94% in era III (1997-2000, P <.05). The 2-year recurrence rates in these 2 periods were 42% and 8% (P <.05). In conclusion, excellent long-term results can be achieved in hepatitis B patients after liver transplantation with modern strategies, and survival rates are similar to other indications. Based on our experience, hepatitis B patients, including those with active viral replication, should not be excluded from liver transplantation.

Correlation of hepatitis B virus load with loss of e antigen and emerging drug-resistant variants during lamivudine therapy

It remains unclear whether sequential assessment of hepatitis B virus (HBV) load during lamivudine therapy can predict the loss of hepatitis B e antigen or emergence of drug-resistant variants. Therefore, a longitudinal study was carried out in 28 consecutive patients with chronic hepatitis B who started lamivudine therapy for a median of 12 months (range, 6-31). HBV DNA copy numbers were determined at 3-month intervals. From month 6 onward, HBV viral load below the detection limit of the PCR was predictive of the loss of envelope antigen (P = 0.043). Continuously detectable HBV DNA during the first 12 months of treatment indicated emergence of drug-resistant variants (P = 0.034). These data suggest that the goal of lamivudine therapy should be complete suppression of serum HBV DNA.

Therapeutic management of hepatitis B-related cirrhosis

Hepatitis B virus (HBV) infection has a world-wide distribution, and may lead to cirrhosis, end-stage liver disease and hepatocellular carcinoma. Therapeutic strategies for HBV cirrhosis are changing rapidly. Treatment with interferon (IFN)-alpha may be hazardous and often can only be administered at low doses. The availability of lamivudine has revolutionized the treatment of chronic hepatitis B and opened up new options for the management of patients with decompensated cirrhosis or recurrent hepatitis B post-liver transplantation. However, lamivudine therapy should be weighed against the risk of selection of resistant mutants and randomized control trials are needed. Hopefully, in the near future, new antiviral drugs such as adefovir dipivoxil which is active on lamivudine-resistant mutants will become available. IFN-alpha is still the only molecule which may prevent HBV-induced hepatocarcinogenesis in humans. Whether other antivirals will also prove useful warrants further follow-up studies.

Late hepatic allograft dysfunction

1. Lifelong monitoring of graft function, immunosuppressive levels, and screening for drug toxicity is required in all liver recipients. 2. Late hepatic allograft dysfunction is common and is caused by a variety of etiologies including rejection, infection, biliary/vascular abnormalities, recurrence of disease, and drug hepatotoxicity. 3. In all patients with late hepatic allograft dysfunction, liver biopsy should be performed to assess for the presence of rejection, and to thus avoid excessive use of bolus corticosteroid therapy and guide appropriate immunosuppressive management. 4. Recurrence of disease is the most common cause of late hepatic allograft dysfunction. 5. Hepatitis C universally reinfects the hepatic allograft, and is associated with decreased patient and graft survival and leads to the recurrence of cirrhosis in 28% of patients within 5 years of transplantation. 6. Major advances have been made in preventing recurrence of hepatitis B by the use of hepatitis B immune globulin in combination with lamivudine therapy. 7. Autoimmune liver diseases such as primary biliary cirrhosis, primary sclerosing cholangitis, and autoimmune hepatitis have a recurrence rate of approximately 20% to 30%. 8. In patients developing recurrence of autoimmune hepatitis, steroid withdrawal is the most common cause. 9. Recurrent hepatocellular cancer can be markedly reduced if strict guidelines are adhered to in selecting patients. 10. Drug hepatotoxicity must always be considered in the differential diagnosis of late hepatic allograft dysfunction.

Preoperative antiviral treatment and postoperative prophylaxis in HBV-DNA positive patients undergoing liver transplantation

BACKGROUND

Despite passive immunoprophylaxis a significant number of patients, especially if hepatitis B virus (HBV) DNA is positive prior to transplantation, develop HBV recurrence. This number might be reduced by lowering viral replication pretransplant with antiviral agents and by postoperative combination of antiviral agents and passive immunoprophylaxis.

PATIENTS AND METHODS

A total of 74 HBV-DNA positive patients who underwent liver transplantation between 9/88 and 4/00 were analyzed retrospectively. Before lamivudine or famciclovir were available, in total 40 patients did not receive any preoperative antiviral therapy. Since 11/93, 17 patients were treated with famciclovir 1500 mg daily, after 4/96 17 patients with lamivudine 150 mg daily prior liver transplantation. Posttransplant all patients received passive immunoprophylaxis aiming at a titer of more than 100 U/liter. In the 34 patients with preoperative antiviral therapy an additional prophylaxis with the respective antiviral agent was applied.

RESULTS

Under preoperative famciclovir and lamivudine 30 and 71% of patients became HBV-DNA negative, respectively. Actuarial reinfection rate 2 years after liver transplantation was 48% without antiviral prophylaxis, which was not statistically different from 55% under perioperative famciclovir therapy. In contrast only 18% developed HBV recurrence under perioperative lamivudine treatment. During both antiviral regimens neither pre nor posttransplant severe side effects were observed.

CONCLUSION

Perioperative application of famciclovir is not recommendable, whereas lamivudine seems to lower recurrence rates significantly. Whether the observed effect is due to pre- or postoperative application remains to be addressed in further studies. In addition the long-term course has to be awaited.

Lamivudine and low-dose hepatitis B immune globulin for prophylaxis of hepatitis B reinfection after liver transplantation possible role of mutations in the YMDD motif prior to transplantation as a risk factor for reinfection

BACKGROUND/AIMS

Reinfection with hepatitis B virus (HBV) after liver transplantation (OLT) is associated with an unfavourable clinical course. Lamivudine/hepatitis B immune globulin (HBIG) combination treatment reduces reinfection rates. However, it is unclear at what time point lamivudine should be started and which HBIG doses are sufficient.

METHODS

Twenty-one patients receiving combination treatment were studied. Lamivudine was started up to 16.5 months before OLT and continued thereafter. HBIG was started intraoperatively and continued according to anti-HBs-titers. Median follow-up after OLT was 20 months.

RESULTS

Eleven patients received lamivudine pretreatment for >2 (median 6) months due to initial HBV-DNA-positivity (median 749 pg/ml). After initial lamivudine response HBV-DNA increased in two of them to concentrations above 10 pg/ml prior to OLT. Both had developed mutations in the YMDD motif and suffered from HBV reinfection 13 and 75 days postoperatively. Individual HBIG consumption was highly variable (range 787-4,766 lU/month). Twenty-two percent of anti-HBs titers measured before HBIG administration were below 100 IU/l.

CONCLUSIONS

Combined reinfection prophylaxis with lamivudine and HBIG is effective in patients with controlled viral replication at the time of OLT. However, pretransplantation lamivudine resistance is a risk factor for reinfection. Low dose HBIG maintenance therapy individualized according to anti-HBs-titers appears to be tenable.

Prevention of hepatitis B virus recurrence after liver transplantation in cirrhotic patients treated with lamivudine and passive immunoprophylaxis

BACKGROUND/AIMS

Treatment with hepatitis B virus immune globulins (HBIG) or lamivudine has reduced the rate of hepatitis B recurrence after liver transplantation to approximately 50%.

METHODS

To further decrease hepatitis B recurrence, 33 hepatitis B virus (HBV)-related cirrhotic patients were treated with lamivudine before liver transplantation and with lamivudine together with low-dose HBIG (46 500 IU the first month followed by 5,000 lU/monthly) after surgery.

RESULTS

While on lamivudine, serum HBV DNA level decreased significantly in all patients and in 11 (33%) the Child-Pugh score improved. Twenty-six patients were transplanted. Among the 25 who survived for longer than 12 months, only one (4%) experienced a hepatitis B recurrence over an average follow-up of 31 months, a rate significantly lower (P = 0.0002) than the 50% recurrence rate among a historical control group of 12 patients. However, low-level HBV replication was detected sporadically throughout the follow-up in 64% of patients.

CONCLUSIONS

Over the medium-term, combined prophylaxis with lamivudine and HBIG significantly decreases the risk of hepatitis B recurrence after liver transplantation. Though low-level HBV infection recurred in two thirds of patients, the pathogenic expression of HBV was prevented.

Liver transplantation of patients in end-stage cirrhosis

The success of liver transplantation has resulted in its widespread use for end-stage liver disease; 1- and 5-year survival rates of 70-90% and 60-80% respectively have been reported. Indications for assessment for liver transplantation are now evidence-based and early referral is recommended, correlating with improved patient survival. The management of patients on the waiting list for liver transplantation is designed to prevent complications of liver disease and to avoid therapeutic misadventures. Following transplantation, rejection and infection dominate post-operative complications, and improvements in their prevention and treatment have also correlated with improved patient survival. The development and introduction into clinical practice of a variety of immunosuppressive agents has offered a bewildering array of therapeutic options but with a lack of evidence on which to select optimal immunosuppression. Similarly, difficulties remain in the treatment of some of the complications arising from liver transplantation such as recurrence of disease and complications of immunosuppression.

An open-label study of lamivudine for chronic hepatitis B in six patients with chronic renal failure before and after kidney transplantation

OBJECTIVE

The course of hepatitis B virus (HBV) infection after kidney transplantation is aggressive, with a high mortality rate from liver disease mainly in patients who were serum hepatitis B e antigen (HBeAg) or HBV DNA-positive before transplantation. Lamivudine has been shown to be a potent inhibitor of HBV replication. The aim of the study was to examine the efficacy and safety of lamivudine therapy in patients with chronic renal failure and chronic HBV infection.

METHODS

The study population consisted of six potential candidates for kidney or combined kidney and liver transplantation aged 25-49 yr (four patients had already undergone a kidney transplantation and developed chronic rejection). All were serum HBeAg and/or HBV DNA-positive and had been maintained on hemodialysis for 3 months to 3 yr. The duration of HBV infection was 7 months to 14 yr. Serum alanine aminotransferase (ALT) levels ranged from 72 to 610 U/L (median, 158 U/L). Liver histological evaluation showed mild to moderate chronic hepatitis (n = 4) or liver cirrhosis (n = 2). None of the patients was infected with hepatitis C or D viruses. In four patients, treatment consisted of 10 mg of oral lamivudine per day. In the other two patients, a virological and biochemical response could be achieved only when the dose was increased to 40 mg/day.

RESULTS

Lamivudine treatment was associated with 1) normalization of serum ALT levels and rapid disappearance of serum HBV DNA (by hybridization) (five patients, one of whom died from sepsis); 2) seroconversion: disappearance of HBeAg (three patients) and HBsAg (two patients); 3) minor side effects: abdominal pain and nausea (one patient); 4) clinically asymptomatic lamivudine resistance 8 months after treatment (one patient); and 5) successful combined kidney and liver transplantation with no evidence of recurrent HBV infection at 6-8 months postoperatively (two patients with cirrhosis).

CONCLUSIONS

Lamivudine therapy is effective as an HBV replication inhibitor in patients with chronic renal failure and HBV infection. Prospective studies of lamivudine pharmacokinetics and dosing in renal failure are needed to be able to treat patients appropriately. Although our study is small and further follow-up is needed, our data suggest that lamivudine therapy may enable selected patients with chronic hepatitis B to undergo kidney or combined kidney and liver transplantation in patients with established cirrhosis.

Lamivudine without HBIg for prevention of graft reinfection by hepatitis B: long-term follow-up

BACKGROUND

This open, multicenter study was conducted to evaluate the efficacy and safety of lamivudine prophylaxis given to chronic hepatitis B virus-(HBV) infected patients before and after orthotopic liver transplantation (OLT). We now present long-term data that follow our previous short-term report.

METHODS

Twenty-three patients were treated with lamivudine (100 mg orally, daily); 13 (57%), were serum HBV DNA positive (Abbott Genostics, Abbott Laboratories, Chicago, IL) at study entry. Patients received lamivudine for at least 4 weeks before OLT, and for up to 50 months (median 25 months) after OLT.

RESULTS

Of the 23 treated patients, 17 survived to undergo OLT. Eleven patients (65%) survived up to 4 years (median 36 months) after OLT. One of the survivors stopped lamivudine because of a possible adverse reaction 9 months post-OLT, and prophylaxis with HBV immune globulin was then established. Ten survivors continue lamivudine. Eight long-term survivors have normal liver function without evidence of HBV reinfection. Of the 17 transplanted patients, 6 died. Four patients died (3 days to 5 months post-OLT) without evidence of graft reinfection. Two further patients died at 19 and 23 months post-OLT from graft failure. Both patients had YMDD variant detected at 12 months post-OLT. Two other patients with YMDD-variant HBV remain alive on lamivudine, 9 and 15 months after development of the variant.

CONCLUSIONS

Lamivudine, given before and after OLT, prevents significant graft reinfection for the majority of treated patients. The study has also shown that lamivudine is extremely well tolerated by liver failure patients and for a prolonged period after transplantation.

Development of resistance and perspectives for future therapies against hepatitis B infections: lessons to be learned from HIV

Several first-generation nucleoside analogues have been tested against chronic hepatitis B virus (HBV) infection, but trials were unsuccessful or accompanied by toxicity. Recently, oral second-generation nucleoside analogues have been developed that have potent activity against HBV. The best-studied compound so far is lamivudine ((-)2'-deoxy-3'-thiacytidine; 3TC). Lamivudine is an inhibitor of reverse transcriptase (RT) activity and is in clinical use in human immunodeficiency virus (HIV)-infected individuals. As several studies on the use of lamivudine for hepatitis B show, the development of resistance in the viral polymerase under lamivudine treatment, however, causes a significant clinical problem. All other drugs in advanced clinical development for HBV are nucleosides; cross-resistance is therefore expected in most cases. The history of HIV treatment demonstrates that new classes of drugs, the protease inhibitors and non-nucleosidic inhibitors of RT, allowed for a longer-term clinical benefit when used in combination with nucleoside analogues. The development of non-nucleosidic compounds with different modes of action therefore appears very important for the treatment of chronic hepatitis B as well.

Combination low-dose hepatitis B immune globulin and lamivudine therapy provides effective prophylaxis against posttransplantation hepatitis B

Although antiviral prophylaxis with lamivudine monotherapy appears to reduce post-liver transplantation recurrence of hepatitis B virus (HBV) infection, breakthrough infections occur in at least 20% of the patients because of the development of drug resistance. Combined lamivudine and intravenous hepatitis B immune globulin (HBIG) therapy (10,000-IU doses) may reduce this risk, but its use is limited by cost ( approximately US $45,000/yr) and availability. We report the experience at liver transplant centers in Australia and New Zealand in which lamivudine has been used in combination with much lower doses of HBIG than used in conventional HBIG prophylaxis. Lamivudine, 100 mg/d, was administered to hepatitis B surface antigen (HBsAg)-positive candidates on listing for transplantation and was continued posttransplantation. HBIG, 400 or 800 IU, was administered intramuscularly (IM) daily for 1 week from transplantation and monthly thereafter. Thirty-seven HBsAg-positive patients underwent transplantation using this protocol. Thirty-six of these patients were HBV DNA positive by polymerase chain reaction (PCR) or hybridization assay. Thirty-four patients had chronic HBV, 2 patients had hepatitis B and C, and 1 patient had hepatitis B, C, and D. Five patients died within 1 month of transplantation and are not included in the analysis. Mean follow-up in the remaining 32 patients was 18.4 months (range, 5 to 45 months). Treatment was well tolerated, with no significant adverse events. Thirty-one of 32 patients were HBsAg negative, and all 32 patients were HBV DNA negative by PCR at latest follow-up. The cost of treatment was US $967 for lamivudine and between $2,290 and $4,480/yr for IM HBIG. Lamivudine and low-dose HBIG treatment prevents posttransplantation recurrence of hepatitis B and is likely to be more cost-effective than high-dose HBIG regimens.

Predictive factors for response to lamivudine in chronic hepatitis B

BACKGROUND

Lamivudine has been shown to be an efficient drug for chronic hepatitis B (CHB) treatment.

AIM

To investigate predictive factors of response, using a quantitative method with high sensitivity.

METHODS

We carried out a prospective trial of lamivudine in 35 patients with CHB and evidence for viral replication, regardless to their HBeAg status. Lamivudine was given for 12 months at 300 mg daily and 150 mg thereafter. Response was considered when DNA was undetectable by PCR after 6 months of treatment. Viral replication was monitored by end-point dilution PCR. Mutation associated with resistance to lamivudine was detected by DNA sequencing in non-responder patients.

RESULTS

Response was observed in 23/35 patients (65.7%) but only in 5/15 (33.3%) HBeAg positive patients. Only three pre-treatment variables were associated to low response: HBeAg (p = 0.006), high viral load (DNA-VHB > 3 x 10(6) copies/ml) (p = 0.004) and liver HBcAg (p = 0. 0028). YMDD mutations were detected in 7/11 non-responder patients.

CONCLUSIONS

HBeAg positive patients with high viral load show a high risk for developing drug resistance. On the other hand, HBeAg negative patients show a good response to lamivudine even with high viremia.

Lamivudine after hepatitis B immune globulin is effective in preventing hepatitis B recurrence after liver transplantation

The prevention of recurrent hepatitis B virus (HBV) infection after orthotopic liver transplantation (OLT) with hepatitis B immunoglobulin (HBIG) is expensive and requires indefinite parenteral administration. Lamivudine is a nucleoside analogue capable of inhibiting HBV replication. The aim of this study is to determine the efficacy of lamivudine in the prevention of recurrent HBV infection after a course of HBIG in patients who were hepatitis B surface antigen (HBsAg) positive and hepatitis Be antigen (HBeAg) negative before OLT. Patients at high risk for recurrent HBV infection (HBeAg positive and HBV DNA positive) were excluded. Thirty HBsAg-positive, HBeAg-negative patients underwent OLT from January 1993 to June 1997. All 30 patients were administered HBIG after OLT and, after 2 years, were given the option of continuing with HBIG or switching to lamivudine. Five patients were excluded: 3 patients were lost to follow-up and 2 patients died of technical complications. Three patients terminated HBIG therapy at 8, 24, and 29 months after OLT, and reinfection with HBV occurred in 1 patient. Six patients elected to continue HBIG therapy for life; 1 patient died of melanoma and the remaining 5 patients are HBsAg negative, with an average follow-up of 73 months. Sixteen patients were converted to lamivudine after a course of HBIG, and all 16 patients are HBsAg negative, with an average follow-up of 51 months after OLT. Five patients have been on lamivudine monotherapy for more than 24 months. These results suggest that lamivudine administered after a posttransplantation course of HBIG can effectively prevent the recurrence of HBV infection in patients who are HBsAg positive and HBeAg negative before OLT.

Indications for liver transplantation in patients with chronic hepatitis B and C virus infection and hepatocellular carcinoma

Patients with chronic hepatitis B virus (HBV) infection were not accepted for liver transplantation in Asia in the past because the hepatitis B immune globulin (HBIG) used to prevent post-transplantation recurrence was very expensive and it was generally believed that Asians with hepatitis B fared worse than Caucasians after liver transplantation. The availability of lamivudine has altered the indication of liver transplantation for these patients. Twenty-five Chinese patients with chronic HBV infection were given lamivudine as primary prophylaxis against HBV re-infection before transplantation. Five patients died within 40 days of transplantation. After a median follow-up period of 14 months (range, 5-39), 17 patients had lost serum HBsAg from 4 days to 27 months post transplantation, but it reappeared in three patients 4-12 months later. Antibody to HBsAg was detected periodically in the serum of 1 patients who had lost HBsAg. At the last follow-up, six patients were HBsAg-positive and HBV DNA was detected in only one of them. The indication for liver transplantation for chronic hepatitis C virus (HCV) infection is not as strict as for patients with chronic HBV infection because the long-term survival is similar to that of non-hepatitis C patients, even though re-infection by HCV in the recipients is nearly universal. The main issue in the selection of patients with HCV for liver transplantation is therefore identification of criteria that can predict re-infection and development of cirrhosis. These include factors such as multiple episodes of rejection, use of OKT3, pre-transplant viral load and genotype, but reports are not consistent and so there are no well-defined selection criteria. The selection criteria for patients with hepatocellular carcinoma are now well defined. Many studies have confirmed that a tumour > 5 cm, and showing vascular invasion, and poor differentiation adversely affects survival. In practice, only patients with a tumour < 5 cm and Child's C cirrhosis are accepted for liver transplantation. Transarterial oily chemoembolization and intralesional alcohol injection are used to control or down-stage the tumour while patients wait for a cadaveric liver graft.

Liver transplantation

Survival after liver transplantation has steadily improved, in part because of newer immunosuppression, which may offer decreased long-term side effects. Reduction of steroids early in the course of transplant continues to be a goal, with satisfactory results in terms of both risk of rejection and reduction of side effects. Dominating the literature and the press in 1999 was the controversy surrounding the way in which livers are allocated. Regulation by the federal government was proposed to change the way the United Network of Organ Sharing distributes and allocates livers. Prompted by the shortage of organs, living-donor liver transplantation has blossomed. Continued experience in pediatric patients has shown excellent survival rate and quality of life. In adults, further experience is being gained with respect to the use of right lobes for transplantation. Early data suggest that this is a potential alternative to cadaveric transplantation in adults, with acceptable risk to the donor. Despite advances made in improving the technical aspects of transplantation, recurrent disease remains a significant issue. Lamivudine appears to be a potent inhibitor of hepatitis B virus DNA replication after liver transplantation, although resistance remains a significant problem. Further review of transplantation for hepatitis C virus is encouraging, with excellent five-year survival rate. However, studies evaluating the evolution of fibrosis in these patients throw caution on those results, showing increased progression to cirrhosis over time. Further follow-up of these patients is needed to more accurately assess long-term impact of hepatitis C on morbidity and mortality rates after liver transplantation.

Liver transplantation

Since the first human liver transplant done in 1963, the procedure has become a routine procedure with an excellent outcome in terms both of quality and of length of survival. The development and introduction into clinical practice of a variety of immunosuppressive agents has given the clinician a bewildering array of therapeutic options but with a lack of evidence on which to select for optimal immunosuppression. Tolerance can be reliably achieved in some animal transplants but remains to be achieved in humans. One of the major challenges facing the transplant community is the shortage of donor organs: imaginative approaches to overcome this problem include more effective use of marginal donor livers, splitting livers and development of living related transplants. While advances have been made in the field of xenotransplantation, there remain many hurdles to be overcome before this approach can be introduced into human transplantation. In the meanwhile, there are difficulties in determining the optimal criteria for listing patients for transplantation and for treating some of the complications arising after transplantation such as recurrence of disease and complications of immunosuppression, e.g. renal failure, malignancy and vascular disease.

Outcome of lamivudine resistant hepatitis B virus infection in the liver transplant recipient

BACKGROUND

In many transplant centres lamivudine is an important component of prophylaxis against, and treatment of, hepatitis B virus (HBV) graft infection. Drug resistant HBV species with specific polymerase mutations may emerge during lamivudine treatment.

AIMS

To examine the clinical consequences of graft infection by lamivudine resistant virus.

METHODS

The clinical course of four liver transplant patients who developed graft infection with lamivudine resistant virus was reviewed. The response of HBV infection to reduction of immunosuppression and to manipulation of antiviral therapy was assessed. For each patient, serum viral titre was measured and the viral polymerase gene was sequenced at multiple time points.

RESULTS

High serum titres were observed following emergence of the lamivudine resistant species. Wild type HBV re-emerged as the dominant serum species after lamivudine withdrawal. All patients developed liver failure, and onset of liver dysfunction was observed when resistant virus was the dominant serum species. In three patients, liver recovery was observed when immunosuppression was stopped and when alternative antivirals were given. Wild type virus appeared to respond to ganciclovir, and to reintroduction of lamivudine. For one patient, introduction of famciclovir was associated with clinical, virological, and histological response.

CONCLUSIONS

Failure of lamivudine prophylaxis may identify patients at special risk for the development of severe graft infection. Treatment of graft reinfection should include reduction of immunosuppression, and systematic exposure to alternative antivirals. Viral quantitation and genetic sequencing are essential components of therapeutic monitoring.

Significance testing of clinical data using virus dynamics models with a Markov chain Monte Carlo method: application to emergence of lamivudine-resistant hepatitis B virus

Bayesian analysis using a virus dynamics model is demonstrated to facilitate hypothesis testing of patterns in clinical time-series. Our Markov chain Monte Carlo implementation demonstrates that the viraemia time-series observed in two sets of hepatitis B patients on antiviral (lamivudine) therapy, chronic carriers and liver transplant patients, are significantly different, overcoming clinical trial design differences that question the validity of non-parametric tests. We show that lamivudine-resistant mutants grow faster in transplant patients than in chronic carriers, which probably explains the differences in emergence times and failure rates between these two sets of patients. Incorporation of dynamic models into Bayesian parameter analysis is of general applicability in medical statistics.